Such wrench devices for screwing up to a set amount of torque are commonly referred to as "torque wrenches". Torque wrenches are used, inter alia, for screwing stoppers onto the tops of bottles when packaging liquid or powder substances on a mass production line. Another use for torque wrenches is doing up nuts on a mass production line.
Conventional torque wrenches have spindles fitted with mechanically controlled moving jaws, with the torque being measured by a friction clutch or by a magnetic drive. In either case, the maximum applied torque is adjustable, either by suitably compressing a spring, or else by moving magnets to change a magnetic field. When the predetermined torque is reached, the clutch slips until a jaw-opening command is applied, which generally takes place after a predetermined screwing time has elapsed.
Torque wrench spindles also exist having jaws which open automatically when the desired torque is reached, with the torque being measured by a complex spring-release device integrated in the torque wrench spindle.
All of the above-mentioned devices require the torque wrench spindle to be stopped in order to change the torque setting, and if the torque wrench forms a part of a high throughput machine having a plurality of torque wrench spindles, each spindle must be set individually. Workers operating such machines generally find this to be inconvenient, and in addition, productivity is reduced by any period for which the machine is stopped. Furthermore, when a friction clutch is used, clutch slipping leads to progressive wear or heating, and thus to reduce accuracy in torque setting.
One aim of the present invention is to provide a torque wrench device which is of simple structure and which has operating characteristics that remain constant regardless of conditions of use.
Another aim of the present invention is to provide a torque wrench device suitable for fitting to a multi-spindle machine, such that the torque of all of the spindles can be set together by a single common adjustment.